Lubricants in commercial use today are prepared from a variety of natural and synthetic base stocks admixed with various additive packages depending upon their intended application. The base stocks typically include mineral oils, polyalphaolefins (PAO), gas-to-liquid base oils (GTL), silicone oils, phosphate esters, diesters, polyol esters, and the like.
A major trend for industrial engine oils is an overall improvement in quality as higher quality base stocks become more readily available. Typically the highest quality industrial products are formulated with base stocks such as PAOs or GTL stocks.
One problem facing producers of high viscosity index PAOs is that of reducing the unsaturation of the as-polymerized carbon chains of the PAO products, which can be quantified by Bromine Number (ASTM D1159). A PAO fluid cannot be satisfactorily used as a lubricant base stock if its Bromine Number exceeds 3. The unsaturation indicated by higher Bromine Number can result in poor oxidative stability and poor high temperature stability of the PAO molecules. Accordingly, it is typical to hydrogenate these as-polymerized PAO products in order to reduce the level of unsaturation in the molecules, so as to render them suitable for use as lubricant base stocks. WO 2007/011462 discloses post-polymerization hydrogenation in order to produce a PAO having a Bromine Number of less than 2. Current commercial high viscosity PAOs, such as PAO100 and PAO150, are hydrogenated to improve the oxidative stability of the base stocks.
The hydrogenation step is expensive and is difficult for thicker materials such as fluids above viscosity of 300 cSt at 100° C. In addition, terminal unsaturation present in as-polymerized PAOs can lead to oxidation and degradation of the product. There is an unmet need in the art to optimize the polymerization reaction and functionalization process for producing functional PAOs, so as to avoid the need for expensive, post-polymerization hydrogen finishing, such that the functional PAO product is suitable for use as a lubricant base stock.
Further, there is a need for high viscosity (300-900 cSt at 100° C.) fluids for industrial lubes. There is a need for very high viscosity products (300-900 cSt at 100° C.) with very high viscosity index (VI), low pour points and fluids with narrow molecular weight distribution and high oxidative stability. The present disclosure provides solutions to these problems, which shall become apparent as described below.